Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
  • H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/30—Resource management for broadcast services
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/04—Wireless resource allocation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
  • H04W48/12—Access restriction or access information delivery, e.g. discovery data delivery using downlink control channel
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/12—Wireless traffic scheduling
  • H04W72/121—Wireless traffic scheduling for groups of terminals or users
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W76/00—Connection management
  • H04W76/10—Connection setup

Definitions

• Embodiments of the present invention are directed to multicasting within a wireless communications system and more particularly to multicasting to a plurality of access terminals over a dynamically selected downlink channel within the wireless communications system.
• Wireless communication systems have developed through various generations, including a first-generation analog wireless phone service (1 G), a second-generation (2G) digital wireless phone service (including interim 2.5G and 2.75G networks) and a third-generation (3G) high speed data / Internet-capable wireless service.
• a first-generation analog wireless phone service (1 G) a second-generation (2G) digital wireless phone service (including interim 2.5G and 2.75G networks)
• a third-generation (3G) high speed data / Internet-capable wireless service There are presently many different types of wireless communication systems in use, including Cellular and Personal Communications Service (PCS) systems.
• Examples of known cellular systems include the cellular Analog Advanced Mobile Phone System (AMPS), and digital cellular systems based on Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), the Global System for Mobile access (GSM) variation of TDMA, and newer hybrid digital communication systems using both TDMA and CDMA technologies.
• CDMA Code Division Multiple Access
• FDMA Fre
• CDMA mobile communications was standardized in the United States by the Telecommunications Industry Association/Electronic Industries Association in TIA/EIA/IS-95-A entitled "Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System," referred to herein as IS-95.
• Combined AMPS & CDMA systems are described in TIA/EIA Standard IS-98.
• Other communications systems are described in the IMT-2000/UM, or International Mobile Telecommunications System 2000/Universal Mobile Telecommunications System, standards covering what are referred to as wideband CDMA (WCDMA), CDMA2000 (such as CDMA2000 IxEV-DO standards, for example) or TD-SCDMA.
• WCDMA wideband CDMA
• CDMA2000 such as CDMA2000 IxEV-DO standards, for example
• TD-SCDMA TD-SCDMA
• AN access network
• RAN radio access network
• IP Internet Protocol
• Push-to-talk (PTT) capabilities are becoming popular with service sectors and consumers.
• PTT can support a "dispatch" voice service that operates over standard commercial wireless infrastructures, such as CDMA, FDMA, TDMA, GSM, etc.
• a dispatch model communication between endpoints (ATs) occurs within virtual groups, wherein the voice of one "talker" is transmitted to one or more "listeners.”
• a single instance of this type of communication is commonly referred to as a dispatch call, or simply a PTT call.
• a PTT call is an instantiation of a group, which defines the characteristics of a call.
• a group in essence is defined by a member list and associated information, such as group name or group identification.
• a transmission of data to a single destination is referred to as "unicast”.
• a “broadcast” refers to a transmission of data packets to all destinations or access terminals (e.g., within a given cell, served by a given service provider, etc.), while a “multicast” refers to a transmission of data packets to a given group of destinations or access terminals.
• the given group of destinations or "multicast group” may include more than one and less than all of possible destinations or access terminals (e.g., within a given group, served by a given service provider, etc.). However, it is at least possible in certain situations that the multicast group comprises only one access terminal, similar to a unicast, or alternatively that the multicast group comprises all access terminals (e.g., within a cell or sector), similar to a broadcast.
• Broadcasts and/or multicasts may be performed within wireless communication systems in a number of ways, such as performing a plurality of sequential unicast operations to accommodate the multicast group, allocating a unique broadcast/multicast channel (BCH) for handling multiple data transmissions at the same time and the like.
• BCH broadcast/multicast channel
• a conventional system using a broadcast channel for push-to-talk communications is described in United States Patent Application Publication No. 2007/0049314 dated March 1 , 2007 and entitled “Push-To-Talk Group Call System Using CDMA Ix-EVDO Cellular Network", the contents of which are incorporated herein by reference in its entirety.
• a broadcast channel can be used for push-to-talk calls using conventional signaling techniques.
• the use of a broadcast channel may improve bandwidth requirements over conventional unicast techniques, the conventional signaling of the broadcast channel can still result in additional overhead and/or delay and may degrade system performance.
• 3GPP2 The 3 rd Generation Partnership Project 2 (“3GPP2") defines a broadcast- multicast service (BCMCS) specification for supporting multicast communications in CDMA2000 networks. Accordingly, a version of 3GPP2's BCMCS specification, entitled “CDMA2000 High Rate Broadcast-Multicast Packet Data Air Interface Specification", dated February 14, 2006, Version 1.0 C.S0054-A, is hereby incorporated by reference in its entirety.
• BCMCS broadcast- multicast service
• An access network determines to transmit multicast messages on a downlink shared channel.
• the access network receives a multicast registration message and a traffic channel request from at least one access terminal.
• the access network assigns a traffic channel to the at least one access terminal, and transmits the multicast messages on the downlink shared channel.
• the access network can determine a channel type upon which the support a multicast session, can indicate the channel type selection to the at least one access terminal in an announce message and can then transmit the multicast messages for the multicast session on the selected channel type.
• the at least one access terminal receives the announce message, requests a traffic channel and receives a traffic channel assignment, registers to the multicast session and monitors the downlink shared channel for multicast messages.
• FIG. 1 is a diagram of a wireless network architecture that supports access terminals and access networks in accordance with at least one embodiment of the invention.
• FIG. 2 illustrates the carrier network according to an example embodiment of the present invention.
• FIG. 3 is an illustration of an access terminal in accordance with at least one embodiment of the invention.
• FIG. 4A illustrates a multicast call-setup process for a multicast session to be carried on a downlink broadcast channel (BCH) in both target and supporting sectors according to an embodiment of the present invention.
• BCH downlink broadcast channel
• FIG. 4B illustrates a cluster formed during the process of FIG. 4A.
• FIG. 5A illustrates a multicast call-setup process for a multicast session to be carried on a downlink control channel (CCH) in target sectors according to an embodiment of the present invention.
• CCH downlink control channel
• FIG. 5B illustrates a cluster formed during the process of FIG. 5A.
• FIG. 5C illustrates an example of a control channel cycle of the downlink CCH.
• FIG. 6A illustrates a process for updating a cluster formed in accordance with FIG. 4A according to an embodiment of the present invention.
• FIGS. 6B and 6C illustrates clusters at different stages of the update process of FIG. 6A.
• FIG. 7A illustrates a process for updating a cluster formed in accordance with FIG. 5A according to an embodiment of the present invention.
• FIGS. 7B and 7C illustrate clusters at different stages of the update process of FIG. 7.
• a High Data Rate (HDR) subscriber station referred to herein as an access terminal (AT) may be mobile or stationary, and may communicate with one or more HDR base stations, referred to herein as modem pool transceivers (MPTs) or base stations (BS).
• An access terminal transmits and receives data packets through one or more modem pool transceivers to an HDR base station controller, referred to as a modem pool controller (MPC), base station controller (BSC) and/or packet control function (PCF).
• Modem pool transceivers and modem pool controllers are parts of a network called an access network.
• An access network transports data packets between multiple access terminals.
• the access network may be further connected to additional networks outside the access network, such as a corporate intranet or the Internet, and may transport data packets between each access terminal and such outside networks.
• An access terminal that has established an active traffic channel connection with one or more modem pool transceivers is called an active access terminal, and is said to be in a traffic state.
• An access terminal that is in the process of establishing an active traffic channel connection with one or more modem pool transceivers is said to be in a connection setup state.
• An access terminal may be any data device that communicates through a wireless channel or through a wired channel, for example using fiber optic or coaxial cables.
• An access terminal may further be any of a number of types of devices including but not limited to PC card, compact flash, external or internal modem, or wireless or wireline phone.
• the communication link through which the access terminal sends signals to the modem pool transceiver is called a reverse link or traffic channel.
• the communication link through which a modem pool transceiver sends signals to an access terminal is called a forward link or traffic channel.
• traffic channel can refer to either a forward or reverse traffic channel.
• FIG. 1 illustrates a block diagram of one exemplary embodiment of a wireless system 100 in accordance with at least one embodiment of the invention.
• System 100 can contain access terminals, such as cellular telephone 102, in communication across an air interface 104 with an access network or radio access network (RAN) 120 that can connect the access terminal 102 to network equipment providing data connectivity between a packet switched data network (e.g., an intranet, the Internet, and/or carrier network 126) and the access terminals 102, 108, 110, 112.
• RAN radio access network
• the access terminal can be a cellular telephone 102, a personal digital assistant 108, a pager 110, which is shown here as a two-way text pager, or even a separate computer platform 112 that has a wireless communication portal.
• Embodiments of the invention can thus be realized on any form of access terminal including a wireless communication portal or having wireless communication capabilities, including without limitation, wireless modems, PCMCIA cards, personal computers, telephones, or any combination or sub-combination thereof.
• access terminal including a wireless communication portal or having wireless communication capabilities, including without limitation, wireless modems, PCMCIA cards, personal computers, telephones, or any combination or sub-combination thereof.
• wireless modems PCMCIA cards
• personal computers personal computers, telephones, or any combination or sub-combination thereof.
• the terms “access terminal”, “wireless device”, “client device”, “mobile terminal” and variations thereof may be used interchangeably.
• System 100 is merely exemplary and can include any system that allows remote access terminals, such as wireless client computing devices 102, 108, 110, 112 to communicate over-the-air between and among each other and/or between and among components connected via the air interface 104 and RAN 120, including, without limitation, carrier network 126, the Internet, and/or other remote servers.
• remote access terminals such as wireless client computing devices 102, 108, 110, 112 to communicate over-the-air between and among each other and/or between and among components connected via the air interface 104 and RAN 120, including, without limitation, carrier network 126, the Internet, and/or other remote servers.
• the RAN 120 controls messages (typically sent as data packets) sent to a base station controller/packet control function (BSC/PCF) 122.
• the BSC/PCF 122 is responsible for signaling, establishing, and tearing down bearer channels (i.e., data channels) between a packet data service node 160 ("PDSN") and the access terminals 102/108/110/112. If link layer encryption is enabled, the BSC/PCF 122 also encrypts the content before forwarding it over the air interface 104.
• the function of the BSC/PCF 122 is well-known in the art and will not be discussed further for the sake of brevity.
• the carrier network 126 may communicate with the BSC/PCF 122 by a network, the Internet and/or a public switched telephone network (PSTN).
• PSTN public switched telephone network
• the BSC/PCF 122 may connect directly to the Internet or external network.
• the network or Internet connection between the carrier network 126 and the BSC/PCF 122 transfers data, and the PSTN transfers voice information.
• the BSC/PCF 122 can be connected to multiple base stations (BS) or modem pool transceivers (MPT) 124.
• BS base stations
• MPT modem pool transceivers
• the BSC/PCF 122 is typically connected to the MPT/BS 124 by a network, the Internet and/or PSTN for data transfer and/or voice information.
• the MPT/BS 124 can broadcast data messages wirelessly to the access terminals, such as cellular telephone 102.
• the MPT/BS 124, BSC/PCF 122 and other components may form the RAN 120, as is known in the art. However, alternate configurations may also be used and the invention is not limited to the configuration illustrated.
• the functionality of the BSC/PCF 122 and one or more of the MPT/BS 124 may be collapsed into a single "hybrid" module having the functionality of both the BSC/PCF 122 and the MPT/BS 124.
• FIG. 2 illustrates the carrier network 126 according to an embodiment of the present invention. In the embodiment of FIG.
• the carrier network 126 includes a packet data serving node (PDSN) 160, a broadcast serving node (BSN) 165, an application server 170 and an Internet 175.
• application server 170 and other components may be located outside the carrier network in alternative embodiments.
• the PDSN 160 provides access to the Internet 175, intranets and/or remote servers (e.g., application server 170) for mobile stations (e.g., access terminals, such as 102, 108, 110, 112 from FIG. 1 ) utilizing, for example, a cdma2000 Radio Access Network (RAN) (e.g., RAN 120 of FIG. 1 ).
• RAN Radio Access Network
• the PDSN 160 may provide simple IP and mobile IP access, foreign agent support, and packet transport.
• the PDSN 160 can act as a client for Authentication, Authorization, and Accounting (AAA) servers and other supporting infrastructure and provides mobile stations with a gateway to the IP network as is known in the art. As shown in FIG. 2, the PDSN 160 may communicate with the RAN 120 (e.g., the BSC/PCF 122) via a conventional A10 connection.
• the A10 connection is well-known in the art and will not be described further for the sake of brevity.
• the broadcast serving node (BSN) 165 may be configured to support multicast and broadcast services.
• the BSN 165 will be described in greater detail below.
• the BSN 165 communicates with the RAN 120 (e.g., the BSC/PCF 122) via a broadcast (BC) A10 connection, and with the application server 170 via the Internet 175.
• the BCA10 connection is used to transfer multicast and/or broadcast messaging. Accordingly, the application server 170 sends unicast messaging to the PDSN 160 via the Internet 175, and sends multicast messaging to the BSN 165 via the Internet 175.
• the RAN 120 transmits multicast messages, received from the BSN 165 via the BCA10 connection, over a broadcast channel (BCH) of the air interface 104 to one or more access terminals 200.
• BCH broadcast channel
• an access terminal 200 (here a wireless device), such as a cellular telephone, has a platform 202 that can receive and execute software applications, data and/or commands transmitted from the RAN 120 that may ultimately come from the carrier network 126, the Internet and/or other remote servers and networks.
• the platform 202 can include a transceiver 206 operably coupled to an application specific integrated circuit ("ASIC" 208), or other processor, microprocessor, logic circuit, or other data processing device.
• ASIC 208 or other processor executes the application programming interface ("API') 210 layer that interfaces with any resident programs in the memory 212 of the wireless device.
• API' application programming interface
• the memory 212 can be comprised of read-only or random-access memory (RAM and ROM), EEPROM, flash cards, or any memory common to computer platforms.
• the platform 202 also can include a local database 214 that can hold applications not actively used in memory 212.
• the local database 214 is typically a flash memory cell, but can be any secondary storage device as known in the art, such as magnetic media, EEPROM, optical media, tape, soft or hard disk, or the like.
• the internal platform 202 components can also be operably coupled to external devices such as antenna 222, display 224, push-to-talk button 228 and keypad 226 among other components, as is known in the art.
• an embodiment of the invention can include an access terminal including the ability to perform the functions described herein.
• the various logic elements can be embodied in discrete elements, software modules executed on a processor or any combination of software and hardware to achieve the functionality disclosed herein.
• ASIC 208, memory 212, API 210 and local database 214 may all be used cooperatively to load, store and execute the various functions disclosed herein and thus the logic to perform these functions may be distributed over various elements.
• the functionality could be incorporated into one discrete component. Therefore, the features of the access terminal in FIG. 3 are to be considered merely illustrative and the invention is not limited to the illustrated features or arrangement.
• the wireless communication between the access terminal 102 and the RAN 120 can be based on different technologies, such as code division multiple access (CDMA), WCDMA, time division multiple access (TDMA), frequency division multiple access (FDMA), Orthogonal Frequency Division Multiplexing (OFDM), the Global System for Mobile Communications (GSM), or other protocols that may be used in a wireless communications network or a data communications network.
• CDMA code division multiple access
• WCDMA time division multiple access
• FDMA frequency division multiple access
• OFDM Orthogonal Frequency Division Multiplexing
• GSM Global System for Mobile Communications
• the data communication is typically between the client device 102, MPT/BS 124, and BSC/PCF 122.
• the BSC/PCF 122 can be connected to multiple data networks such as the carrier network 126, PSTN, the Internet, a virtual private network, and the like, thus allowing the access terminal 102 access to a broader communication network.
• voice transmission and/or data can be transmitted to the access terminals from the RAN using a variety of networks and configurations. Accordingly, the illustrations provided herein are not intended to limit the embodiments of the invention and are merely to aid in the description of aspects of embodiments of the invention.
• a target sector is any sector within a wireless communications system, having (or expected to have) at least one multicast group member, that carries a multicast flow for a given multicast session
• a supporting sector is any sector within the wireless communications system, that is not expected to have multicast group members, and also carries the multicast flow (e.g., to enable soft combining in target sectors for high-data rate multicast communications).
• Target and supporting sector behavior is discussed in more detail within co-pending U.S. Patent Application no.
• FIG. 4A illustrates a multicast call-setup process for a multicast session to be carried on a downlink BCH in both target and supporting sectors according to an embodiment of the present invention.
• the application server 170 e.g., a Qchat or Push-to-Talk (PTT) server
• receives a request to initiate a multicast session e.g., from a PTT initiator, not shown.
• the application server 170 forwards an announce message to the RAN 120 for transmission to access terminals ("multicast group members", e.g., ATs 1 ...N) that belong to a multicast group of the multicast session.
• multicast group members e.g., ATs 1 ...N
• the application server 170 can forward the announce message to the RAN 120 through the BSN 165 via a BCA10 connection.
• the RAN 120 receives the announce message over the BCA10 connection and transmits the announce message to ATs 1...N over the air interface 104 (e.g., as a data-over-signaling (DOS) message addressed to the multicast group on the downlink CCH, via a standard paging of ATs 1 ...N, etc.).
• DOS data-over-signaling
• ATs 1 ...N receive the announce message and one or more of ATs 1 ...N register for the multicast session, 415 (e.g., by transmitting a BCMCSFIowRegistration message) and send an announce acknowledgment (ACK) that the RAN 120 forwards to the application server 170.
• ACK announce acknowledgment
• FIG. 4B illustrates an example cluster (i.e., a set of target and supporting sectors) that may be formed in 420 of FIG. 4A.
• FIG. 4B assumes that ATs A... G have registered for the multicast session, that ATs A... G reside in target sectors T1 through T4, respectively, and that target sectors T1 through T4 are supported by supporting sectors S1 through S12.
• Cluster origination is described in greater detail within the above-incorporated co-pending patent entitled "MULTICAST COMMUNICATIONS WITHIN A WIRELESS COMMUNICATIONS NETWORK".
• the RAN 120 transmits a scheduling message (e.g., a broadcast overhead message (BOM)) in the target and supporting sectors, 425.
• a scheduling message e.g., a broadcast overhead message (BOM)
• BOM can include an advertisement of the announced multicast session, along with information instructing ATs 1 ...N on how to tune to the multicast session on the downlink BCH (e.g., an interlace-multiplex (IM) pair on the downlink BCH upon which multicast messages for the multicast session are to be transmitted).
• IM interlace-multiplex
• BOMs transmitted in target sectors are configured to suppress subsequent AT registrations (e.g., to reduce traffic, except for when the RAN 120 wants to confirm the status of the target sectors), and BOMS transmitted in supporting sectors are configured to prompt AT registrations (e.g., so that the RAN 120 can transition the supporting sector to a target sector, as discussed below in greater detail). Accordingly, the ATs 1...N that have received the BOM tune to the indicated IM pair and monitor for the multicast messages, 430.
• the application server 170 begins forwarding multicast messages (e.g., multicast media messages, such as video, audio, text, etc.) to the RAN 120 via the BSN 165 over the BCA10 connection for transmission to ATs 1 ...N.
• multicast messages e.g., multicast media messages, such as video, audio, text, etc.
• the RAN 120 receives the multicast messages over the BCA10 connection and transmits the multicast messages to ATs 1...N over the air interface 104 on the BOM-indicated IM pair of the downlink BCH, in both the target and supporting sectors.
• the ATs 1 ...N that have tuned to the BOM-indicated IM pair of the downlink BCH receive and decode the multicast messages, 445.
• transmitting multicast messages in supporting sectors to be used for soft combining for access terminals within the target sectors helps the access terminals decode high-data rate broadcasts or multicasts.
• the access terminals may not necessarily need to soft combine with the supporting sector transmssion to decode the multicast successfully.
• multicast group members are not geographically densely located (e.g., there are not a high number of multicast group members in any particular target sector)
• the potentially large number of supporting sectors may decrease an overall spectral efficiency because many sectors are transmitting redundant information to reach only a few local multicast group members.
• the RAN 120 waits for the BOM- indicated IM pair on the downlink BCH for the transmission.
• delay or lag is introduced for the duration the RAN 120 waits before the transmission on a next IM pair.
• FIG. 5A illustrates a multicast call-setup process for a multicast session to be carried on a downlink CCH in one or more target sectors according to an embodiment of the present invention.
• the application server 170 e.g., a Qchat or Push-to-Talk (PTT) server
• receives a request to initiate a multicast session e.g., from a PTT initiator, not shown.
• the application server 170 forwards the announce message to the RAN 120 for transmission to ATs 1 ...N that belong to a multicast group of the multicast session.
• the application server 170 can forward the announce message to the RAN 120 through the BSN 165 via a BCA10 connection.
• the RAN 120 receives the announce message over the BCA10 connection and determines a channel type (e.g., BCH, CCH, etc.) upon which to support the multicast session associated with the announce message. For example, the RAN 120 can determine between the downlink CCH and BCH based at least in part upon estimated locations of the multicast group members for the announced multicast session. The locations of the multicast group members can be tracked during operation of the wireless communications system 100, and the RAN 120 can maintain a location table that indicates the last known position of the multicast group members based on route update reports received from the multicast group members. Location tracking of access terminals is discussed in more detail within co-pending U.S. Patent Application no.
• a channel type e.g., BCH, CCH, etc.
• the information contained within the location table can be used to decide between multicasting on the downlink BCH or CCH.
• the BCH-based multicasting discussed with respect to FIG. 4A-4B can be implemented (e.g., to reduce a likelihood of overloading the CCH), in an example, and the process may advance to 410 of FIG. 4A.
• the process may advance to 515 and the CCH may be used.
• the CCH has a lower data rate (e.g., 76.8 kbps) then the BCH (e.g., 307.2 kbps).
• the determination of 510 can be based at least in part upon a data rate associated with the multicast session. For example, if the expected data rate of the multicast session is above a data rate threshold, then the RAN 120 may select or determine to carry the multicast session on the BCH. Otherwise, if the expected data rate of the multicast session is not above a data rate threshold, then the RAN 120 may select or determine to carry the multicast session on the CCH.
• the CCH may be selected to increase the decoding success rate of the multicast messages.
• the RAN 120 may select the BCH to avoid overloading the CCH.
• any combinaton of data rate, loading and/or AT- position criteria may be used to determine the channel type for the multicast transmission.
• the RAN 120 may apply a weighting function to the data rate, loading and sector co-location factors to make the determination of 510.
• the determination of 510 can be RNC or subnet specific, such that different subnets can carry the multicast session on different channel types. For example, if conditions in a first subnet are better for the CCH and conditions in a second subnet are better for the BCH, the RNCs in charge of the different subnets need not synchronize the channel types, and can rather independently determine the best channel type to use on a per-subnet basis.
• the determination of 510 can be specific to given groups of sectors within a particular subnet.
• a first group or set of sectors within a subnet can be configured to carry a multicast session on the downlink CCH, while another group of sectors within the same subnet can be configured to support the multicast session on the downlink BCH.
• the RAN 120 determines to transmit the multicast session on the CCH, and the process advances to 515.
• the RAN 120 configures the announce message to be transmitted to ATs 1 ...N to indicate that the announced multicast session will be carried on the CCH.
• the RAN can attach a StorageBlobAssignment message to the announce message that includes a flag indicating the CCH for multicast transmission (e.g., in QChat, the StorageBlobAssignment message can contain an access control message (ACM) with a 'transmission mode' field set to indicate CCH or BCH, in an example).
• ACM access control message
• the configured announce message is transmitted over the air interface 104, 520 (e.g., as a mobile-termination data over signaling (MT-DOS) message, or via a standard paging process).
• the transmission of the announce message can be based at least in part on a location table maintained at the RAN 120 for tracking multicast group member locations (e.g., MT-DOS announce in proximity to the ATs' expected locations, and standard paging announce in other sectors).
• MT-DOS mobile-termination data over signaling
• the transmission of the announce message can be based at least in part on a location table maintained at the RAN 120 for tracking multicast group member locations (e.g., MT-DOS announce in proximity to the ATs' expected locations, and standard paging announce in other sectors).
• an initial or estimated target sector set can be established to more efficiently announce the multicast session.
• ATs 1 ...N receive the configured announce message, 525, and interpret the announce message as indicating a multicast transmission on the downlink CCH.
• each of ATs 1 ...N that are interested in participating in the announced multicast session requests a traffic channel (TCH), 530, from the RAN 120 (e.g., by sending a ConnectionRequest message).
• TCH traffic channel
• the RAN 120 assigns the requested TCHs to each requesting AT, 535.
• the TCH assigned to ATs 1 ...N allows the RAN 120 to track the precise locations of ATs 1 ...N (e.g., during handoffs between sectors) based on messaging from ATs 1 ...N that is transmitted on a reverse link portion of the assigned TCH.
• the assigned reverse TCH is not used by ATs 1 ...N to send media for transmission to other multicast group members.
• ATs 1 ...N may transmit keep-alive packets so the RAN 120 does not de-allocate the TCHs, and also RouteUpdate messages for location tracking and/or to request handoff.
• the TCH may be assigned for purposes of location tracking and/or handoff, it will be appreciated that the downlink portion of the TCH (F-TCH) may be substantially silent, unless the AT is engaged in a separate unicast session using the assigned TCH.
• the F-TCH does not necessarily consume forward link resources (i.e., timeslots), while the R-TCH permits location tracking of the AT by the RAN 120.
• one or more of ATs 1 ...N register for the multicast session, 415 (e.g., by transmitting a BCMCSFIowRegistration message) and also send an announce acknowledgment (ACK) that the RAN 120 forwards to the application server 170.
• ACK announce acknowledgment
• the scheduling message or BOM need not be transmitted because each AT monitors the CCH continuously, and each AT need not be informed of a designated IM pair on the BCH because the multicast session is being carried on the CCH.
• the TCH request of 530 can be bundled with the announce ACK and multicast registration requests of 540 in at least one embodiment.
• the RAN 120 determines the target sectors for the multicast session, 550.
• step 550 may generate an initial set of target sectors for the multicast session.
• step 550 may update an already existing set of target sectors that are determined prior to transmission of the announce message in 520 (e.g., based on a location table for tracking the multicast group members, as discussed above).
• the RAN 120 need not determine supporting sectors for the multicast session because the low data-rate of the CCH is easier for ATs to decode, and as such the overhead associated with the supporting sectors can be reduced or omitted because soft combining may not be necessary.
• FIG. 5B illustrates an example cluster (i.e., with only target sectors) that may be formed in 550 of FIG. 5A.
• FIG. 5B assumes that ATs A... G have registered for the multicast session, and that ATs A... G reside in target sectors T1 through T4.
• the supporting sectors S1 through S12 need not be included in the cluster.
• the application server 170 After the application server 170 receives a first announce ACK for the multicast session, the application server 170 begins forwarding multicast messages (e.g., multicast media messages, such as video, audio, text, etc.) to the RAN 120 via the BSN 165 over the BCA10 connection for transmission to one or more of ATs 1 ...N.
• the RAN 120 receives the multicast messages over the BCA10 connection and schedules the multicast messages on the CCH.
• the multicast messages can be scheduled on an asynchronous control channel capsule of a given control channel cycle of the CCH, as will now be described in greater detail with respect to FIG. 5C.
• FIG. 5C illustrates an example of a control channel cycle of the downlink CCH.
• each control channel cycle includes a total of 256 slots.
• Each control channel cycle includes a synchronous control channel capsule (SC), a plurality of asynchronous control channel capsules (ACs), and a plurality of sub- synchronous control channels (SSCs).
• SC synchronous control channel capsule
• ACs asynchronous control channel capsule
• SSCs sub- synchronous control channels
• Each SC may include a plurality of control channel MAC layer packets, whereas each AC includes only one control channel MAC layer packet, in an example.
• interference e.g., inter-cell interference
• a different offset is applied to the SC for each MPT/BS 124 to avoid collisions.
• the MPT/BS may transmit as many as three SSC capsules within one control channel period or 256 slot cycle. Each SSC typically transmits only one control channel MAC layer packet. Assuming an offset value of 2, the SSCs are transmitted at time slots 66, 130 and 194. Unlike SCs and SSCs, ACs can start anytime within a control channel cycle. Therefore, messages sent on ACs do not need to wait for pre-defined time slots.
• Control channel capsules e.g., SCs, ACs, SSCs, etc.
• BCMCS systems as such a further description thereof has been omitted for the sake of brevity.
• the RAN 120 transmits the multicast messages to ATs 1...N over the air interface 104 on the CCH as scheduled in 560, in each target sector.
• the ATs 1 ...N monitor the CCH and received the multicast transmissions, 570.
• the number of supporting sectors can be reduced and/or eliminated by using the CCH to carry the multicast flow for given multicast session.
• cluster adjustments e.g., the addition or removal of target/supporting sectors
• the RAN 120 receives the registration message and updates the cluster based on the knowledge that AT G has left sector T4 and entered sector S7, 625.
• target sector T4 is removed from the set of target sectors (i.e., because no multicast group members are present), supporting sector S7 is transitioned to a target sector T5 and added to the set of target sectors, and the set of supporting sectors is updated to account for the loss of target sector T4 and addition of target sector T5.
• FIG. 6C illustrates an example of the updated cluster of 625.
• the RAN 120 transmits the multicast messages for the multicast session on the downlink BCH within the target and supporting sectors of the updated cluster.
• Handoff (e.g., soft handoff, hard handoff, etc.) is well known in the art.
• the inter-sector handoff of AT G is possible because AT G was previously assigned a TCH in 535 of FIG. 5A.
• the RAN 120 Because the RAN 120 has handed off AT G from target sector T4 to the new sector, the RAN 120 is aware of AT G's new location, and can update a location table that tracks AT locations with AT G's new position. Further, the RAN 120 updates the cluster by ceasing transmission of multicast messages in target sector T4 and transitioning target sector T4 to a non- target sector (e.g., because no multicast group members remain in T4 after AT G leaves), 715, and transitions AT G's new sector to target sector T5.
• 7C illustrates an example of the updated cluster of 715/720 of FIG. 7A.
• the RAN 120 transmits the multicast messages for the multicast session on the downlink CCH within the target sectors of the updated cluster, which are monitored by AT G, 730.
• the determining step of 510 of FIG. 5A may also be performed during an active multicast session, and not merely in advance of an announce message transmission.
• the RAN 120 can toggle a multicast session back and forth between the BCH and CCH based on current operating parameters, in an example (e.g., if the number of multicast group members rises above or falls below a threshold during operation, etc.). Because there is overhead associated with this type of dynamic switching, the thresholds associated with an active-session channel switch may be different than the thresholds associated with 510 of FIG. 5A.
• a spectral efficiency of the wireless communications system 100 can be increased by transmitting a multicast flow primarily within target sectors on a low data-rate shared downlink channel, such as the downlink CCH.
• This allows fewer (e.g., zero) supporting sectors to be deployed (e.g., within a particular subnet, within all subnets carrying the session, within a subnet portion constituting a given group of sectors within the subnet while another subnet portion of the same subnet includes supporting sectors, etc.) that carry the multicast flow even though no target ATs are present within the supporting sectors.
• the RAN 120 can track the locations of ATs based on the assigned TCH, such that ATs do not drop the multicast session when handing off to sectors that are not yet carrying the multicast flow.
• embodiments are generally directed to supporting a multicast session in one or more subnets on a downlink control channel instead of a downlink broadcast channel.
• the downlink control channel transmits at a lower- data rate than the downlink broadcast channel, and as such soft-combining is less likely to be necessary as compared to the downlink broadcast channel.
• the multicast session can be supported on a downlink shared channel that can correspond to either the control channel or the broadcast channel.
• the downlink shared channel corresponds to the downlink broadcast channel
• soft-combining via one or more supporting sectors can still be omitted so long as a traffic channel is assigned to each non-floorholder AT for location tracking during the multicast session (e.g., so the session is not dropped if an AT hands off to a non-target sector).
• an error rate of the downlink BCH embodiment without supporting sectors may be higher than an error rate if the session were supported on the downlink CCH, it will also be appreciated that carrying the session on the downlink BCH reduces the load on the downlink CCH.
• DSP digital signal processor
• ASIC application specific integrated circuit
• FPGA field programmable gate array
• a general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine.
• a processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
• a software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD- ROM, or any other form of storage medium known in the art.
• An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium.
• the storage medium may be integral to the processor.
• the processor and the storage medium may reside in an ASIC.
• the ASIC may reside in a user terminal (e.g., access terminal).
• the processor and the storage medium may reside as discrete components in a user terminal.
• the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium.
• Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another.
• a storage media may be any available media that can be accessed by a computer.
• such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.
• any connection is properly termed a computer-readable medium.
• the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave
• the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.
• Disk and disc includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

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